I can't believe you aren't kidding. No, the classes aren't all perfectly balanced, open your ******* eyes. For example, the Pyro's flamethrower has less than 5 times the DPS compared to the Heavy's minigun, it also has less DPS compared to almost every other non-melee weapon in the game. Justify that.

Competitive play is enitrely different. You also don't ever see anything but the base weapons in competitive play, but there are some unlockables clearly better than the base weapons. Tf2 was designed completely for casual play with no competitive scene in mind.

It really depends on the situation. In midfights pyros aren't that great and generally our team's (I play highlander competitive) pyro stays near me and whoever I'm healing, just to deter jumpers and scouts/spies. However, in areas which aren't too open, pyros can be scary. The Axtinguisher is a REALLY nasty surprise when you walk around a corner. Also, Soldiers and demos can be unpleasantly surprised by a good pyro.